The invention relates generally to copper and other metal vapor lasers, and more particularly, to wicks used in such lasers for recirculation of condensed metal vapor.
A metal vapor laser, e.g., copper (CVL), operates by passing a current through a metal vapor within a refractory tube, exciting the metal atom electrons to specific energy levels, then emitting energy when stimulated by the passage of specific energy photons. The refractory tube is heated either by the discharge current or an external heat source. Copper or other metal is placed in the discharge tube at a point where a given steady state temperature will exist. The copper vaporizes and fills the discharge tube to the equilibrium partial pressure for copper at the source temperature. The discharge tube is filled with a buffer gas, e.g., helium or neon, at sub-atmospheric pressure, to provide an electrical conduction path through the discharge tube and to control copper transport. The buffer gas pressure is such that the copper atoms are in a highly collisional diffusion regime. Copper that collides with the refractory wall on the hot side of the source remains as a vapor, whereas collisions on the cool side result in condensation of the vapor. This condensed copper does not contribute to the laser operation unless it can be returned to the source region. Thus, a wick is used to condense copper and transport it to the source region.
In a metal vapor laser, particularly copper vapor laser or gold vapor laser, the metal vapor condenses on the cold end of the wick and is carried back to the hot region by capillary action. Through various loss mechanisms, the copper is depleted and the lifetime of the laser is less than a few hundred hours. The conventional wick oxidizes and cannot be wet by the condensing copper; sputtered electrode materials form an oxide coating on the condensed copper to inhibit wicking action.
U.S. Pat. No. 3,654,567 to Hodgson, issued Apr. 4, 1972 describes a vapor discharge cell having wicks for use in a vapor laser. Each wick has an evaporation region and a condensation region; a vapor-liquid circulation cycle is established whereby as the vapor condenses on the condensation region it is pulled by surface tension forces through the wick to the evaporation region where it is re-evaporated.
U.S. Pat. No. 4,247,830 to Karras, et al, issued Jan. 27, 1981 is directed to plasma sprayed wicks for pulsed metal vapor lasers. Improved wicks for recirculating condensed vapor back to the discharge zone of a metal vapor laser are described. The wicks are generally tubular in configuration and may be formed of sintered metal or of a metal substrate with a porous plasma sprayed layer thereon.
Accordingly, it is an object of the invention to provide an improved wick for a copper or other metal vapor laser.
It is also an object of the invention to improve the wicking mechanism in a copper or other metal vapor laser.
It is a further object of the invention to control the chemical environment in the laser to control contaminants to the wick's surface.
It is also an object of the invention to reduce oxides of copper or other metal back to copper or other metal in a copper or other metal vapor laser to prevent loss of the active gain medium in the laser.
It is another object of the invention to provide longer life operation of a copper or other metal vapor laser than has been possible in the previous state of the art.
It is a further object of the invention to provide a useful life in excess of 1000 hours for a copper or other metal vapor laser.